Method of making a coil bobbin

ABSTRACT

A method of making coil bobbins wherein a plurality of bobbins are assembled on an upstanding guide form, while simultaneously gauging the length dimension between the flanges of each bobbin, gauging the squareness of the flanges to the longitudinal dimension of the bobbins, and regauging the openings in the tubular member of each bobbin to its original as formed configuration.

United States Patent Petrinjak et al.

[54] METHOD OF MAKING A COIL BOBBIN [72] lnventors: Emerick J. Petriniak, Masury, Ohio; William J. Grasinger, Stoneboro, Pa.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

[22] Filed: Sept. 15, 1969 [21] Appl. No.: 857,962

[52] US. Cl. ..156/90, 29/605, 156/288, 156/304, 242/118.41, 336/198, 336/208, 156/391 [51] Int. Cl ..B29d 3/00, H01f 27/02, H01f 27/28 [58] Field oiSeareh ..336/198, 208; 269/47,48,48.1, 269/52; 29/470.1, 472.1; 242/118.4, 118.41, 118.7;

[56] References Cited UNITED STATES PATENTS 1,958,840 5/ 1934 Baker ..242/ 1 18.7 1,997,641 4/1935 Isenberg. ..336/208 X 2,355,477 8/1944 Stahl ..242/l18.7

[ Feb. 22, 1972 2,368,025 1/ 1945 Jamison ..242/1 18.7 X 2,563,393 8/1951 Buys ..242/118.7 X 3,105,786 10/1963 Anderson ..242/l18.7 X 3,153,519 10/1964 Jewellet al. 242/118 41 X 3,215,905 11/1965 Bloom ..336/208 X 3,348,302 10/ 1967 Foerster.. ..336/208 X 3,428,929 2/1969 Brown et a1. 242/118.41 X 3,488,830 l/197O Miller ..269/48.l X

Pn'mary Examiner-Carl D. Quarforth Assistant Examiner-Roger S. Gaither Attomey-A. T. Stratton, F. E. Browder and D. R. Lackey ABSTRACT A method of making coil bobbins wherein a plurality of bobbins are assembled on an upstanding guide form, while simultaneously gauging the length dimension between the flanges of each bobbin, gauging the squareness of the flanges to the longitudinal dimension of the bobbins, and regauging the openings in the tubular member of each bobbin to its original as formed configuration.

2 Claims, 3 Drawing Figures PAIENTEUFEB22 I872 SHEET 1 [IF 2 INVENTORS Emerick J. Petrinjok and William J. Grosinger ATTQRNE PAIENTED-FEB22 I972 SHEET 2 BF 2 METHOD or MAKING A COIL BOBBIN BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates in general to coils for electrical apparatus, such as control transformers, and more specifically to a method of constructing bobbins for electrical coils.

2. Description of the Prior Art The spoollike form or bobbin about which insulated wire conductor is wound to provide an electrical coil, or coils, such as for control transformers, includes a tubularinsulating portion about which the wire is wound, and insulating flange members at the ends of the tubular portion which define a trough or channel for containing the coil turns. Since the production requirement for small coils of this nature is usually substantial, it is important that the bobbin construction facilitate the manufacture thereof, in order for it to be produced at a relatively low cost. However, the cost objective must not be achieved at the expense of dimensional accuracy in construction. The completed bobbin must have accurate dimensions, and the flanges must be perpendicular to the longitudinal axis of the opening in the bobbin. Further, the dimensional accuracy should be achievable without resorting to costly gauges and fixtures and without requiring a high degree of skill on the part of the assembly personnel.

SUMMARY OF THE INVENTION Briefly, the present invention is a new and improved method of manufacturing coil bobbins, which enables quick, accurate assembly thereof without special operator skills. An upstanding guide form having a cross-sectional configuration which matches the. opening in the coil bobbin is the only fixture required. The first flange of a bobbin is telescoped over the upstanding guide form, and positioned against the flat base of the fixture. Adhesive is applied to the ends of the tubular portion or member of the bobbin, and the tubular member is then telescoped over the guide form until one of its adhesive coated ends butts against the surface of the first flange member. The second flange member is then telescoped over the guide form until the remaining adhesive coated end butts against the second flange member. These steps are then repeated until the desired number of bobbins have been assembled on the same guide form, and then an axial pressure is applied to the stacked bobbins to maintain the tubular members and their associated flanges in firm contact during the step of drying the adhesive. The assembled bobbins are then removed from the guide form. The flanges of adjacent bobbins may be separated on the guide form, to prevent adhesive from one bobbin from contacting an adjacent bobbin, by disposing a thin sheet of material between the bobbins, as they are assembled, with the material selected being of a type which will not strongly bond to the adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of the invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIG. 1 is a perspective view of a control transformer which may utilize a coil bobbin constructed according to the teachings of the invention;

FIG. 2 is a perspective view, shown partially exploded, which illustrates the method of assembling coil bobbins according to the teachings of the invention; and

FIG. 3 is a cross-sectional view of a coil bobbin shown in FIG. 2, taken along the line IIIIII.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, and FIG. 1' in particular, there is shown a perspective view of a control transformer .of the type which may utilize a coil bobbin constructed according to the teachings of the invention. Transformer 10 includes an electrical coil assembly 12 disposed in inductive relation with a magnetic core 14. Electrical coil assembly 12 includes highand low-voltage coils constructed of a plurality of turns of insulated wire, such as enamel coated copper, wound on a coil form or bobbin 16. Bobbin 16 includes a tubular member having an opening 34 extending between its ends, about which the electrical coils are wound, and first and second flange members 18 and 20, respectively, disposed adjacent the ends of the tubular member. One of the flange members, such as flange member 20, contains a plurality of terminals, such as terminals 22, 24, 26 and 28, near one edge of the flange member, and terminals at the opposite edge, such as terminal 30. The high-voltage coil or coils may be connected to the terminals at one edge of the flange member, and the low-voltage coil, or coils, may be connected to the terminals at the opposite edge, to provide physical separation of the highand low-voltage coil leads.

The magnetic core 14 may be of the stacked type shown, having a plurality of magnetic, metallic laminations 32, such as E-I laminations, which encircle the coil assembly 12, as well as having a leg portion 33 which extends through opening 34 in the coil bobbin 16; or, the magnetic core may be of the wound type, as desired.

The coil bobbin 16 must be accurately formed in order to enable the magnetic core 14 to be quickly and easily assembled about the winding assembly 12. It is especially important to provide an accurately dimensioned bobbin, with the dimensions of the bobbins being repeatable from bobbin to bobbin, when automatic stacking equipment is used to stack the laminations of the magnetic core about the coil or winding assembly. For example, the opening 34 in the tubular member must be maintained in the as-formed configuration, without having its edges bent or dented, or otherwise partially collapsed, the length dimension between the flanges is critical, and it is important that the flanges l8 and 20 be paralleled with one another and perpendicular to the longitudinal axis of the tubular member.

FIG. 2 is a perspective view, partially exploded, which illustrates the assembly of bobbins according to the teachings of the invention, which method automatically gauges the length of the bobbins between the flanges, the squareness of the flanges, and regauges the opening in the tubular member of the bobbin to its original configuration and dimensions, in the event that it has been partially collapsed.

More specifically, FIG. 2 illustrates a fixture 40 having a base member 42 and an upstanding guide member 44 secured perpendicularly to the base member, an assembled bobbin l6, and an exploded view of a bobbin 16. Like reference numerals in FIGS. 1 and 2 indicate like components, with the reference numerals on the exploded view of the bobbin including a prime mark to distinguish the two bobbins shown in FIG. 2. At least the outer surface of the upstanding member 44 should be formed of a material to which an adhesive or glue will not strongly adhere, such as polytetrafluoroethylene. This material may be a thin coating applied on the outside surface of upstanding member 44, or the entire upstanding member 44 may be constructed of this material. The base member 42 of fixture 40 may also be formed of the same material, or it may have a coating of the hereinbefore mentioned material applied to at least its upper surface, or it may be protected from coming into contact with adhesive by a thin sheet of material, such as polytetrafluoroethylene, disposed on at least a portion of its upper surface which surrounds the upstanding member 44. Member 44 should have an overall length sufficient to accommodate the number of bobbins to be assembled thereon, such as 18-20 inches for assembling l0 bobbins having an overall length dimension of 1.75 inches.

The component parts of the bobbin 16 shown in FIG. I, i.e., the first end flange 18, the second end flange 20, and a tubular insulating member 46 shown in FIG. 2, are formed in separate manufacturing operations prior to final assembly, with the flange members 18 and 20 being cut from a sheet of a suitable insulating material, such as pressboard, and the tubular member 46 being formed of a suitable insulating material,

such as a plurality of layers of Kraft paper. The first end flange 18 may be conveniently formed of 0.030 inch thick pressboard, while the second flange member 18 should be thicker, such as 0.060 inch thick pressboard, in order to firmly support the terminals, coil leads, and external leads which will be attached thereto.

All of the component parts of bobbin 16 have openings therein which are of the same size and configuration, and the cross-sectional configuration and dimensions of the upstanding member 44 are selected to provide a snug but sliding fit between the upstanding member and the openings defined by the first and second flange members 18 and 20, and the tubular insulating member 46. In this embodiment, the winding leg 33 of magnetic core 14 shown in FIG. 1 is rectangular. Thus, the openings in the component parts of bobbin 16, and the cross-sectional configuration of the upstanding member 44, are also rectangular. As illustrated most clearly in the exploded view of bobbin 16' in FIG. 2, the first flange member 18' has first and second major parallel surfaces joined by a rectangular opening 34, the second flange member has first and second major parallel surfaces joined by a rectangular opening 50, and the tubular member 46 has four sidewall members which define a rectangular opening 52 extending between first and second ends 53 and 55, respectively, of the tubular member. In addition to the major opening 50 in flange member 20', a plurality of additional openings are provided, such as openings 54, 56, 58, 60 and 62, which are used to mount the terminals 22, 24, 26, 28 and 30, respectively, shown in FIG. 1.

The first step in the method of assembling bobbin 16 is to telescope or slide one of the flange members, such as the second flange member 20, over the upstanding guide member 44 of fixture 40. The next step is to apply a suitable adhesive to the first and second ends 53 and 55 of the tubular member 46, such as by control dipping the ends in a pan of adhesive having a controlled depth of adhesive therein. The adhesive is given reference numerals .70 and 72 at ends 53 and 55, respectively, of tubular member 46'. Any adhesive may be used which will provide a high-strength bond between the materials of which the component parts are constructed, which bond will be maintained in the environment intended for the apparatus, through the expected service life of the apparatus, such as a moisture resistant casein glue.

The next step is to telescope or slide tubular member 46 over the upstanding guide member 44, until its second end 55 butts against the upper major surface of flange member 20. It should be noted, as illustrated most clearly in FIG. 3, which is a cross-sectional view of bobbin 16 shown in FIG. 2 taken along the lineIII-III, that the end 55 butts against the upper flat major surface of flange member 20, instead of fitting into the opening 50 of the flange. The importance of this construction will be hereinafter explained./

The next step is to telescope or slide the first flange member 18 over the upstanding member 44, until its lower major surface butts against the upper end 53 of tubular member 46. Again it is important to note that the end 53 butts against a flat major surface of flange member 18, instead of having end 53 extend into the opening 34 of the flange.

The next step is to telescope or slide a thin sheet 80 over the upstanding member 44, with the sheet 80 being constructed of a material to which the adhesive will not strongly bond, such as a 2 mil thick sheet of polytetrafluoroethylene, with the sheet having an opening 82 therein which snugly fits the configuration of the upstanding member 44. Sheet 80 separates adjacent bobbins l6 and 16', preventing the adhesive associated with one bobbin from contacting the other bobbin, precluding the undesirable situation of bonding adjacent bobbins together. The steps of telescoping the flange member 20 over the upstanding member, applying adhesive to the ends of the tubular member 46, telescoping the flange member 18 over the upstanding member, and telescoping the separating means 80 over the upstanding member, are then repeated as hereinbefore described for bobbin 16, to assemble each of the remaining plurality of bobbins on upstanding member 44.

While the step of applying the adhesive has been described relative to applying it to the ends of the tubular member 46, it is to be understood that the adhesive could also be applied to the appropriate major sides of each of the flange members, with its application being confined to the surface immediately adjacent the openings in the flange members.

After the requisite number of bobbins have been assembled on fixture 40, an axially extending pressure is applied to the stack of bobbins during the time the adhesive is drying, to maintain a tight contact between the ends of the flange members and their associated tubular member, to insure a good high-strength bond. This axial pressure may be applied by any suitable means. For example, the fixture 40 may include means, such as pivotable fingers and 92 mounted on the base 42 via rod members 94 and 96. Rod members 94 and 96 may each include two spaced sections threaded into opposite ends of a coupling. After the fingers 90 and 92 are pivoted over the flange of the top bobbin, the coupling may be turned to move the divided rods toward one another to clamp the bobbins into firm assembled relation. The coupling may be calibrated or otherwise marked to provide the desired dimension between the upper surface of the base member 42 and the surfaces of the fingers 90 and 92 which are in contact with the flange of the top bobbin, to insure that the plurality of bobbins will have the desired dimensions. Or, the column of bobbins may be clamped by any suitable pressure means until the clamp reaches a stop which is dimensioned according to the number of bobbins in the stack.

The adhesive may be dried at ambient temperature in still air, or the drying may be accelerated by circulating heated air over the assembled bobbins. In practice, suitable adhesive has been used which dries at ambient temperature to provide a satisfactory bond in about 15 minutes time.

The disclosed method of assembling coil bobbins on fixture 40 has many important advantages. The snug fitting guide fonn 44 regauges any of the tubular members which may have been partially collapsed, or which have had their edges bent, the length of the tubular member 46 between its ends automatically gauges the width of the channel which contains the turns of the coils as they are wound, since it butts against the flat major surfaces of the flange members. The ends'of the tubular members are cut square during their manufacture, which automatically aligns the flange members parallel with one another and perpendicular to the longitudinal axis of the tubular member, and the assembly of the bobbins may be quickly accomplished without any special operator skills. The advantages of constructing the bobbins with the ends of the tubular member butting against the major surfaces of the flange members will now be apparent. If the ends of the tubular member were to extend into the openings of the flange members, the openings in the flange members would necessarily have to be larger than the opening in the tubular member. Thus, it would not be possible to manufacture and assemble a plurality of bobbins on a single upstanding guide fixture, as the guide fixture would not accurately locate the position of the flange members with their larger openings. Each bobbin would have to be assembled in an elaborate fixture, which would be required to gauge distance between the inside surfaces of the two flanges, since the two flanges may now slide toward one another on the outside surface of the tubular member, and the fixture would also be required to align the flanges parallel with one another, and perpendicular to the longitudinal axis of the tubular member, since it would be possible to skew the flanges on the tubular member. Further, butting the ends of the tubular member to the major surfaces of the flange members, as disclosed by the teachings of the invention, greatly relaxes the tolerances between the outer dimension of the tubular member 46 and the dimensions of the openings in the flange members, and it also maintains the adhesive between the parts to be assembled. If the ends of the tubular member were to extend into tight fitting openings in the flange members, the adhesive would be wiped away from the joint. If the tolerances between the outer dimension of the tubular member and the openings in the flange members were such that a gap would exist between the members, a weak bond would result. Thus, the disclosed method of assembling coil bobbins greatly facilitates the manufacture of the bobbins, enabling them to be manufactured at minimum cost, while still insuring accurately dimensioned bobbins, with the dimensions being repeatable from bobbin to bobbin.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative, and not in a limiting sense.

We claim as our invention: 1. A method of constructing electrical coil bobbins having an opening therein, comprising the steps of:

providing an upstanding guide form having the dimensions and configurations of the desired opening in the bobbin,

providing a first flange member having an opening therein which has the dimensions and configuration the same as the desired opening in the bobbin,

telescoping said first flange member over said upstanding guide form,

providing a tubular member having first and second ends,

telescoping said tubular member over said upstanding guide form,

butting said first flange member against the first end of said tubular member,

providing a second flange member having an opening therein which has the dimensions and configuration the same as the desired opening in the bobbin,

telescoping said second flange member over said upstanding guide form,

butting said second flange member against the second end of said tubular member,

providing an adhesive between the first and second ends of said tubular member and the surfaces of the flange members they abut,

progressively assembling a plurality of additional tubular and flange members over said upstanding guide form to provide additional bobbins,

clamping the assembly to secure the position of said members,

drying the adhesive to bond said tubular and flange members together,

unclamping the assembly, and

removing the assembled bobbins from said upstanding guide form.

2. The method of claim 1 including the step of telescoping separating members over the guide form between the flange members of adjacent bobbins, to insure that the adhesive on each tubular member bonds only the tubular member to its associated first and second flange members. 

1. A method of constructing electrical coil bobbins having an opening therein, comprising the steps of: providing an upstanding guide form having the dimensions and configurations of the desired opening in the bobbin, providing a first flange member having an opening therein which has the dimensions and configuration the same as the desired opening in the bobbin, telescoping said first flange member over said upstanding guide form, providing a tubular member having first and second ends, telescoping said tubular member over said upstanding guide form, butting said first flange member against the first end of said tubular member, providing a second flange member having an opening therein which has the dimensions and configuration the same as the desired opening in the bobbin, telescoping said second flange member over said upstanding guide form, butting said second flange member against the second end of said tubular member, providing an adhesive between the first and second ends of said tubular member and the sUrfaces of the flange members they abut, progressively assembling a plurality of additional tubular and flange members over said upstanding guide form to provide additional bobbins, clamping the assembly to secure the position of said members, drying the adhesive to bond said tubular and flange members together, unclamping the assembly, and removing the assembled bobbins from said upstanding guide form.
 2. The method of claim 1 including the step of telescoping separating members over the guide form between the flange members of adjacent bobbins, to insure that the adhesive on each tubular member bonds only the tubular member to its associated first and second flange members. 